Half-bridge module

ABSTRACT

The invention relates to a half-bridge module which is arranged in an electrically insulating cooling liquid and in which two semiconductor switches form a half-bridge; the first semiconductor switch is capable of being connected by its source terminal to a high voltage potential, and the second semiconductor switch is capable of being connected by its drain terminal to a low voltage potential; the drain terminal of each first semiconductor switch is connected to the source terminal of the respective second semiconductor switch; whereby respective first semiconductor switches are arranged with their source terminal on a common first metallic conductor rail which is capable of being connected to the high voltage potential; respective second semiconductor switches are arranged with their source terminal on a second metallic conductor rail constituting the output which is arranged alongside the first conductor rail, spaced therefrom; each second semiconductor switch is connected by its drain terminal to a common third metallic conductor rail which is capable of being connected to the low voltage potential and is arranged alongside the first and second conductor rails, spaced therefrom; a capacitor arrangement comprises a backup capacitor which is connected to the first and third conductor rails and which overlaps the first and second semiconductor switches in such a manner that the semiconductor switches are spatially located between the corresponding conductor rails and the backup capacitor; a control input comprises a terminal for connection to the triggering device in the region of a first front side of the conductor rails, and the output comprises a terminal in the region of a second front side of the second conductor rail.

DESCRIPTION

[0001] The invention relates to a half-bridge module for the switching of electrical outputs, which is arranged in a housing containing an electrically insulating cooling liquid and in which at least two semiconductor switches are connected in series, forming a half-bridge. Each semiconductor switch comprises a control input for connection to a triggering device. The first semiconductor switch is capable of being connected by its source terminal to a high voltage potential, and the second semiconductor switch is capable of being connected by its drain terminal to a low voltage potential. For the purpose of forming an output, the drain terminal of each first semiconductor switch is connected to the source terminal of the respective second semiconductor switch. In addition, at least one capacitor arrangement is arranged between the high voltage potential and the low voltage potential. Such a half-bridge module is known from DE-A-42 30 510.

[0002] Half-bridge arrangements of such a type are used for the purpose of forming inverters for highly diverse fields of application, e.g. for feeding induction machines, permanent-magnet motors and such like (see also, for example, DE-A-40 27 969).

[0003] From U.S. Pat. No. 5,132,896 an inverter arrangement is known which, with a view to reducing the effect of distributed inductances of the conductors that are used for connecting the capacitors and the semiconductor switches, comprises lamellar supply lines having a large area. By this means, large damping capacitors for compensating the line inductances are avoided. In addition, the radiation of heat can be improved by virtue of the large-area design of the lamellar supply lines. Furthermore, the lamellar supply lines are designed in such a way that the magnitude and the direction of the flow of current through the lamellar supply lines minimise the effect of the distributed inductances.

[0004] However, with this inverter arrangement the large-area supply lines serve merely to lessen interfering inductances and are employed as supply lines leading to large electrolytic capacitors.

[0005] In order to increase further the power density of the half-bridge module described in the introduction and in order to make it still more suitable, in particular, for large-scale use, said half-bridge module has been developed further to the effect that respective first semiconductor switches are arranged with their source terminal on a common first metallic conductor rail which is capable of being connected to the high voltage potential, and respective second semiconductor switches are arranged with their source terminal on a common second metallic conductor rail constituting the output, the second conductor rail being arranged alongside the first conductor rail, spaced therefrom. Moreover, each second semiconductor switch is connected by its drain terminal to a common third metallic conductor rail which is capable of being connected to the low voltage potential and is arranged alongside the first and second conductor rails, spaced therefrom. The capacitor arrangement comprises a backup capacitor which is connected to the first and third conductor rails by terminals and which overlaps the first and second semiconductor switches in such a manner that the semiconductor switches are spatially located between the corresponding conductor rails and the backup capacitor. In addition, the control input comprises a terminal for connection to the triggering device in the region of a first front side of the conductor rails, and the output comprises a terminal for connection to an electrical load in the region of a second front side of the second conductor rail located opposite the first front side.

[0006] By virtue of the structure, according to the invention, of the half-bridge module, a particularly compact arrangement is achieved which enables a packaging density that cannot be equalled by previous solutions. Hence both the requisite volume of cooling liquid, relative to the total volume, can be kept small and a miniaturisation of the overall arrangement can be achieved that permits use of the invention to become very economical also in mobile applications. In this regard a considerable role is also played by the fact that, by virtue of the structure utilising the third dimension, a spatial separation of the power-conducting lines (or conductor rails) and terminals, on the one hand, and of the triggering lines, on the other hand, is made possible. This results in considerably enhanced immunity to interference. A further significant aspect of the invention is the modular structure, which permits problem-free expansion and adaptation of the half-bridge module in line with the particular requirements.

[0007] In a preferred embodiment the semiconductor switches are constituted by fast-switching, low-loss field-effect transistors (FETs) or by fast-switching, low-loss bipolar transistors with insulated gate terminal (IGBTs). In particular, MOSFETs with integrated freewheeling diodes or additional external freewheeling diodes connected to the transistors in parallel can be employed. These external freewheeling diodes are advantageously arranged in the same manner as the semiconductor switches and in the immediate vicinity of the latter on one of the conductor rails.

[0008] Electrically conducting spacers are arranged on the first and third conductor rails, in particular for the mechanical and electrical parallel connection of several half-bridge modules. Hence half-bridge modules of the same type can be rigidly coupled to one another, and at the same time the supply of the high and low potentials to all the half-bridge modules that have been coupled in such a manner can be achieved in a straightforward way. In one embodiment of the invention the spacers are realised as separate components, with which the respective conductor rails are connected (screw-coupled, riveted, welded etc). As an alternative to this, the spacers may also be integral with the conductor rails, so that the requisite spacing between the individual half-bridge modules comes about and is also kept constant by direct joining of the respective conductor rails.

[0009] In a preferred embodiment of the invention the first, second and third conductor rails are firmly connected to one another mechanically by an electrically insulating carrier board. As an alternative to this, the first, second and third conductor rails may be firmly connected to one another mechanically by electrically insulating crossmembers which are arranged between the individual conductor rails. The carrier board may also serve to receive conductor tracks in order to supply control signals to the semiconductors or in order to lead out test points or measuring points. The carrier board also serves to receive interconnecting lines between the respective control inputs of the semiconductor switches and the terminal for connection to the triggering device.

[0010] In this case the carrier board is preferably provided with recesses which are dimensioned in such a way that the semiconductors (transistors and diodes) that are directly applied on the conductor rails are exposed at least with their contacting points—that is, they are not covered up by the carrier board. This has the result that the effective overall heights of the semiconductors and of the carrier board are not added. Rather, both are connected directly (at the same level) to the conductor rails. Hence the carrier board serves both for the mechanical connection of the conductor rails amongst themselves and for the electrical wiring arrangement. The connection of the conductor tracks that are arranged on the carrier board to the contacting points of the semiconductors is preferably established by bonding wires.

[0011] As an alternative to this, instead of the carrier board an electrically insulating foil with interconnecting lines between the respective control inputs and the terminal for connection to the triggering device may be arranged on the conductor rails. Since a foil is not suitable to establish a mechanically rigid or firm connection between the individual conductor rails, with a view to producing the necessary strength of the conductor-rail arrangement a connection of the conductor rails on the lateral faces thereof facing one another has to be provided additionally. This can be achieved by means of the aforementioned crossmembers or by means of electrically insulating adhesive.

[0012] In a preferred embodiment of the invention the electrically insulating carrier board or the foil carries current-limiting resistors in the triggering lines for the semiconductor switches, said (gate) resistors being provided between the respective control inputs and the terminal for connection to the triggering device.

[0013] In accordance with the invention, at least two half-bridge modules of the type described above are assigned to one another mechanically and are electrically connected in parallel in order to form a half-bridge arrangement. By virtue of the modular concept according to the invention a simple expansion to higher power outputs is possible. By simple parallel connection of an appropriate number of half-bridge modules or expansion of a half-bridge arrangement by additional half-bridge modules it is also possible to provide a higher power output or number of phases.

[0014] The invention accordingly also relates to a power output stage of a triggering device for a multiphase electric motor, wherein a half-bridge arrangement is provided for each phase of the electric motor, the half-bridge arrangements being arranged alongside one another. In a preferred embodiment of the invention a power output stage of a triggering device for a multiphase electric motor is provided, a control-electronics module being spatially assigned to the power output stage and arranged in the same housing. Hence a particularly compact structure of a functional overall arrangement is created, since in this case both the control-electronics module and the power output stage with their plurality of half-bridge arrangements or half-bridge modules are accommodated in the same cooling medium, and the control lines may also be routed so as to be very short and insensitive to interference.

[0015] The semiconductors that are used for the invention are preferably constituted by fast-switching, low-loss field-effect transistors (FETs) or by fast-switching, low-loss bipolar transistors with insulated gate terminal (IGBTs). In this case several pairs of semiconductor switches connected in series may be connected in parallel. In addition, the semiconductor switches may be constituted by a large number of individual semiconductor-switch modules with, in each case, low switching capacities. Through the use of many semiconductor-switch elements with, in each case, a relatively low switching capacity which are, however, easy to connect in parallel, effective cooling can be achieved, since the many individual components can be reached well by the cooling medium.

[0016] A preferred embodiment of the subject-matter of the invention is illustrated in the drawing.

[0017]FIG. 1 shows an electrical circuit diagram of a half-bridge;

[0018]FIG. 2 shows a half-bridge module in a schematic view from above;

[0019]FIG. 3 shows two joined half-bridge modules from FIG. 2 in a schematic sectional representation along line II-II from the front.

[0020]FIG. 1 shows a half-bridge 10 which comprises four pairs 12 a, 12 b, 12 c, 12 d of n-channel MOSFETs connected in parallel which act as semiconductor switches. In each instance two of the MOSFETs 14, 22; 16, 24; 18, 26; 20, 28 which respectively constitute a pair are connected in series. The first MOSFET 14; 16; 18; 20 of each pair is applied by its source terminal to a high voltage potential V_(SS), and each second MOSFET 22; 24; 26; 28 of each pair is applied by its drain terminal to a low voltage potential V_(DD). In this connection, for the purpose of forming an output A the drain terminal of each of the first MOSFETs 14; 16; 18; 20 and the source terminal of each of the second MOSFETs 22; 24; 26; 28 are connected to one another. A control input 32; 34 is provided for the group of the first MOSFETs 14; 16; 18; 20 and for the group of the second MOSFETs 22; 24; 26; 28, respectively, the gate terminals of the respective MOSFETs being selected via gate resistors 36; 38; 40; 42 and 44; 46; 48; 50, respectively.

[0021] Arranged between the high and the low voltage potentials V_(SS) and V_(DD) is a backup-capacitor arrangement which is constituted by individual backup capacitors 52 a, 52 b, 52 c, 52 d connected in parallel. The implementation of the capacitor arrangement 52 a, 52 b, 52 c, 52 d is described in more detailed manner further below. Triggering of the respective group of MOSFETs is effected with a (pulse-width-modulated) control signal having a switching frequency of more than 20 kHz. The switching frequency preferably amounts to 100 kHz and more.

[0022] As shown in FIG. 2, the first MOSFETs 14; 16; 18; 20 are soldered with their source terminal S on a common first metallic conductor rail 60 which is capable of being connected to the high voltage potential V_(SS). The conductor rail 60 has a profile that is approximately rectangular in cross-section and is produced from copper or a material that conducts electric current and heat similarly well.

[0023] The second MOSFETs 22; 24; 26; 28 are soldered with their source terminal (S) on a common second metallic conductor rail 62 constituting the output A, the second conductor rail 62 being arranged alongside the first conductor rail 60, spaced therefrom. The second conductor rail 62 also has a profile that is approximately rectangular in cross-section and is produced from the same material as the first conductor rail 60.

[0024] The second MOSFETs 22; 24; 26; 28 are respectively connected, via one or more bonding wires 64, by their drain terminals D to a common third metallic conductor rail 66 which is capable of being connected to the low voltage potential V_(DD), the third conductor rail 66 being arranged alongside the second conductor rail 62, spaced therefrom.

[0025] The first MOSFETs 14; 16; 18; 20 are respectively connected, via one or more bonding wires 68, by their drain terminals D to the second conductor rail 62.

[0026] The capacitor arrangement 52 is constituted by several block-like foil capacitors 52 a . . . 52 d which are connected to the first and third conductor rails 60, 66 by step-like connecting plates 72, 74. At their free ends the connecting plates 72, 74 exhibit holes 72 a, 74 a, through which pass screws 96, 98 for fastening the connecting plates 72, 74 between the respective conductor rails and spacers 86, 88. The step-like connecting plates 72, 74 are dimensioned in such a way that the block-like foil capacitors 52 a . . . 52 d overlap the respective first and second semiconductor switches in such a manner that the semiconductor switches are spatially located between the corresponding conductor rails and the respective block-like foil capacitor. In this case a small spacing is also maintained between the semiconductor switches and the foil capacitor, so that the cooling liquid is able to flow through between them. The spacers 86, 88 are dimensioned in such a way that the foil capacitors do not protrude beyond them.

[0027] In the embodiment represented in FIG. 2 the diodes 14 a 28 a shown in FIG. 1 are realised as being integrated within the MOSFETs and are therefore not shown separately. Otherwise, separate diodes 14 a . . . 28 a would be soldered alongside the MOSFETs 14 . . . 28, likewise on the first and second conductor rail 60, 62, respectively.

[0028] In order to make available a separately producible and manageable unit consisting of a half-bridge module, the first, second and third conductor rails 60, 62, 66 are firmly connected to one another mechanically by an electrically insulating carrier board 90. To this end, the carrier board 90 is affixed to the conductor rails on the same surface as the semiconductor switches. The carrier board 90 serves, in addition, to receive interconnecting lines 32, 34 between the respective control inputs G of the semiconductor switches and the pins of the terminal strip 76 for connection to the triggering device.

[0029] As shown in FIG. 2, the respective control inputs G as well as a number of test pins on a terminal strip 76 are led out on the carrier board 90 for connection to a triggering device in the region of a first front side 78 (at the bottom in FIG. 2) of the conductor rails 60, 62, 66, whereas the output A is led out to a terminal 80 for connection to an electrical load in the region of a second front side 82 (at the top in FIG. 2) of the second conductor rail 62 located opposite the first front side 78.

[0030] Gate resistors 36 . . . 50 (see FIG. 1) are also arranged on the carrier board 90 as SMD components (surface-mounted devices) between the respective control inputs G of the MOSFETs and the corresponding pins of the terminal strip 76. Connection of the gate resistors to the control inputs G of the MOSFETs is likewise effected via bonding wires 70.

[0031] As can be seen in FIG. 2, the carrier board 90 exhibits rectangular recesses 92, through which the semiconductor switches or the diodes protrude. Hence the overall structure is relatively flat.

[0032] With a view to forming a half-bridge arrangement, several of the half-bridge modules described above can be firmly connected to one another mechanically and can be electrically connected in parallel. This is illustrated in FIG. 3, wherein two identical half-bridge modules are stacked on top of one another and screw-coupled to one another. As is apparent, the outer conductor rails 60, 66 and also the spacers 86, 88 arranged between them serve for the common supply of current for the semiconductor switches, whereas the outputs A of the individual half-bridge modules are provided separately in series.

[0033] The arrangement shown in FIG. 3 can be connected—for each phase of an electrical connection—via the terminal strip 76 (see FIG. 2) to a common control-electronics module so as to form a compact unit which is accommodated in a common housing. In this case the housing is constructed so as to be fluid-tight and contains the inert cooling medium, e.g. a fluorochlorinated hydrocarbon. 

1. A half-bridge module for the switching of electrical powers, which is arranged in a housing containing an electrically insulating cooling liquid and in which at least two semiconductor switches (14, 22; 16, 24; 18, 26; 20, 28) are connected in series, forming a half-bridge (12 a, 12 b, 12 c, 12 d); each semiconductor switch (14, 22; 16, 24; 18, 26; 20, 28) comprises a control input (G) for connection to a triggering device; the first semiconductor switch (14, 16, 18, 20) is capable of being connected by its source terminal (S) to a high voltage potential (V_(SS)); the second semiconductor switch (22, 24, 26, 28) is capable of being connected by its drain terminal (D) to a low voltage potential (V_(DD)); for the purpose of forming an output (A), the drain terminal (D) of each first semiconductor switch (14, 16, 18, 20) is connected to the source terminal (S) of the respective second semiconductor switch (22, 24, 26, 28); and at least one capacitor arrangement (52) is arranged between the high and the low voltage potentials (V_(SS), V_(DD)); characterised in that respective first semiconductor switches (14, 16, 18, 20) are arranged with their source terminal (S) on a common first metallic conductor rail (60) which is capable of being connected to the high voltage potential (V_(SS)); respective second semiconductor switches (22, 24, 26, 28) are arranged with their source terminal (S) on a common second metallic conductor rail (62) constituting the output (A), the second conductor rail (62) being arranged alongside the first conductor rail (60), spaced therefrom; each second semiconductor switch (22, 24, 26, 28) is connected by its drain terminal (D) to a common third metallic conductor rail (66) which is capable of being connected to the low voltage potential (V_(DD)) and is arranged alongside the first and second conductor rails (60, 62), spaced therefrom; the capacitor arrangement (52) comprises a backup capacitor (52 a . . . 52 d) which is connected to the first and third conductor rails (60, 66) by terminals and which overlaps the first and second semiconductor switches (14, 22; 16, 24; 18, 26; 20, 28) in such a manner that the semiconductor switches are spatially located between the corresponding conductor rails (60, 66) and the backup capacitor (52 a . . . 52 d); the control input (G) comprises a terminal (76) for connection to the triggering device in the region of a first front side (78) of the conductor rails (60, 62, 68), and the output (A) comprises a terminal for connection to an electrical load in the region of a second front side (82) of the second conductor rail (62) located opposite the first front side.
 2. Half-bridge module according to claim 1 , characterised in that electrically conducting spacers (86, 88) are arranged on the first and/or third conductor rails (60, 66).
 3. Half-bridge module according to claim 1 , characterised in that the first, second and third conductor rails (60, 62, 66) are firmly connected to one another mechanically by an electrically insulating carrier board (90).
 4. Half-bridge module according to claim 1 , characterised in that the first, second and third conductor rails (60, 62, 66) are firmly connected to one another mechanically by electrically insulating crossmembers which are arranged between the individual conductor rails.
 5. Half-bridge module according to claim 4 , characterised in that an electrically insulating foil with interconnecting lines between the respective control inputs and the terminal for connection to the triggering device is arranged on the conductor rails (60, 62, 66).
 6. Half-bridge module according to claim 3 , characterised in that the electrically insulating carrier board (90) comprises interconnecting lines between the respective control inputs and the terminal for connection to the triggering device.
 7. Half-bridge module according to claim 3 or 5 , characterised in that the electrically insulating carrier board or the foil carries gate resistors which are provided between the respective control inputs and the terminal for connection to the triggering device.
 8. A half-bridge arrangement, characterised in that at least two half-bridge modules according to one or more of the preceding claims are assigned to one another mechanically and are electrically connected in parallel.
 9. A power output stage of a triggering device for a multiphase electric motor, with devices for feeding each phase with electrical power, the feeding devices for each phase comprising a half-bridge arrangement for switching the electrical power, characterised in that the half-bridge arrangements are half-bridge arrangements according to claim 8 , the half-bridge arrangements being arranged alongside one another.
 10. A power output stage of a triggering device for a multiphase electric motor according to claim 9 , characterised in that a control-electronics module is spatially assigned to the power output stage and arranged in the same housing.
 11. A half-bridge arrangement according to one or more of the preceding claims, characterised in that the semiconductor switches (14, 22; 16, 24; 18, 26; 20, 28) are constituted by fast-switching, low-loss field-effect transistors (FETs) or by fast-switching, low-loss bipolar transistors with insulated gate terminal (IGBTs).
 12. Half-bridge arrangement according to one or more of the preceding claims, characterised in that several pairs of semiconductor switches connected in series are connected in parallel.
 13. Half-bridge arrangement according to one or more of the preceding claims, characterised in that the semiconductor switches are constituted by a large number of individual semiconductor-switch components with, in each case, low switching capacities. 